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Why is solar thermal so rare?

by ars 4y ago

ip26 4y ago
Because photovoltaic got so good & cheap, with no moving parts. In most locales it’s now more cost effective to heat your water with photovoltaic panels & an electric water heater.
- hn_go_brrrrr 4y ago
  More reading on this: https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead https://www.greenbuildingadvisor.com/article/solar-thermal-i...
- zeckalpha 4y ago
  Specifically, a heat pump water heater.
  - xxpor 4y ago
    That usually is true if your electricity is generated by natural gas too and you're comparing it against a gas HWH Rough math is NG -> Electricty is 50% efficient thermally. A heat pump can have a COP of 4.2. 100 * .5 * 4.2 = 210% efficient, thermally A hot water heater powered directly by gas is ~100% efficient thermally.
    - kkfx 4y ago
      Personally I do not care about efficiency: I can't sell energy I produce so the point is just heating the water and the load profile of a classic resistance and the load needs of my houses match normally to heat without the heat-pump (witch have a far limited life respect of a classic resistence)... I use the heat pump mode only when there is little solar for few days where there is not enough overall energy production, otherwise being able to produce 120-130% of the overall consumption (of course ONLY when the Sun shine, so NOT independent as some sell just playing with absolute numbers) why care about efficiency? I can't use the extra energy anyway...
  - ars 4y ago
    So I looked into them because of your comment, and they have a very big drawback of taking a very long time to heat the water. That wouldn't work for me, our water usage tends to be very "peaky" - my system can heat the water almost as fast as you can use it in a shower. Maybe with a very complicated system with an extra large storage tank, and perhaps integrated with the home heat (so a single heat pump). I feel like the tech isn't quite ready yet, and I don't like being a pioneer. It seems like a no brainier if you heat with electricity, but not quite ready yet for those who heat with natural gas. Right now it seems better suited for southern climates.
- lutorm 4y ago
  Not at industry scale, I don't think. At least according to these guys: https://www.absolicon.com/ https://www.absolicon.com/
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kkfx 4y ago
Because nowadays p.v. is cheap enough to heat enough water with far less maintenance costs and potential issues, at least that's my choice: I was undecided for a bit of time if going p.v. only or p.v. + thermal and in the end: - with p.v. I'm formally less efficient BUT in winter/cold but still sunny days my p.v. peak at a certain time for a certain time and my water heater start full power when there is enough energy, a solar thermal system take time to reach a sufficient temperature to make water (glicole) flow; - almost no external maintenance, just panels and wires, no leaks or freeze risks, no pipes etc; - no extra energy to make heat transfer fluid flow, witch means no pump, actually my heater is just an isolated "bowl" with a heat pump + classic electrical resistance and a big spiral pipe inside, so I have even no pressurized tank issues (water expansion) nor legionella problems etc; - for my needs 300l of waters heat also in the winter enough 100% on p.v. except if more than two days without Sun, overall cost is very limited, potentially I can use the optional thermal solar integration with a classic wood burning stove to heat water in emergency conditions. Why bother for thermal solar? With a big pool I understand but except for such case in witch solar anyway can't suffice for more or less large part of the year...

Why is solar thermal so rare?

by ars 4y ago

Why is solar thermal so rare?

ip26 4y ago

Because photovoltaic got so good & cheap, with no moving parts. In most locales it’s now more cost effective to heat your water with photovoltaic panels & an electric water heater.

hn_go_brrrrr 4y ago
More reading on this: https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead https://www.greenbuildingadvisor.com/article/solar-thermal-i...
zeckalpha 4y ago
Specifically, a heat pump water heater.
- xxpor 4y ago
  That usually is true if your electricity is generated by natural gas too and you're comparing it against a gas HWH Rough math is NG -> Electricty is 50% efficient thermally. A heat pump can have a COP of 4.2. 100 * .5 * 4.2 = 210% efficient, thermally A hot water heater powered directly by gas is ~100% efficient thermally.
  - kkfx 4y ago
    Personally I do not care about efficiency: I can't sell energy I produce so the point is just heating the water and the load profile of a classic resistance and the load needs of my houses match normally to heat without the heat-pump (witch have a far limited life respect of a classic resistence)... I use the heat pump mode only when there is little solar for few days where there is not enough overall energy production, otherwise being able to produce 120-130% of the overall consumption (of course ONLY when the Sun shine, so NOT independent as some sell just playing with absolute numbers) why care about efficiency? I can't use the extra energy anyway...
- ars 4y ago
  So I looked into them because of your comment, and they have a very big drawback of taking a very long time to heat the water. That wouldn't work for me, our water usage tends to be very "peaky" - my system can heat the water almost as fast as you can use it in a shower. Maybe with a very complicated system with an extra large storage tank, and perhaps integrated with the home heat (so a single heat pump). I feel like the tech isn't quite ready yet, and I don't like being a pioneer. It seems like a no brainier if you heat with electricity, but not quite ready yet for those who heat with natural gas. Right now it seems better suited for southern climates.
lutorm 4y ago
Not at industry scale, I don't think. At least according to these guys: https://www.absolicon.com/ https://www.absolicon.com/

deleted 4y ago

[deleted]

deleted 4y ago

[deleted]

kkfx 4y ago

Because nowadays p.v. is cheap enough to heat enough water with far less maintenance costs and potential issues, at least that's my choice: I was undecided for a bit of time if going p.v. only or p.v. + thermal and in the end: - with p.v. I'm formally less efficient BUT in winter/cold but still sunny days my p.v. peak at a certain time for a certain time and my water heater start full power when there is enough energy, a solar thermal system take time to reach a sufficient temperature to make water (glicole) flow; - almost no external maintenance, just panels and wires, no leaks or freeze risks, no pipes etc; - no extra energy to make heat transfer fluid flow, witch means no pump, actually my heater is just an isolated "bowl" with a heat pump + classic electrical resistance and a big spiral pipe inside, so I have even no pressurized tank issues (water expansion) nor legionella problems etc; - for my needs 300l of waters heat also in the winter enough 100% on p.v. except if more than two days without Sun, overall cost is very limited, potentially I can use the optional thermal solar integration with a classic wood burning stove to heat water in emergency conditions. Why bother for thermal solar? With a big pool I understand but except for such case in witch solar anyway can't suffice for more or less large part of the year...